Two-year-old Brielle Coutu loves listening to music, dancing and eating enough cheese that her mother, Heather, often wonders aloud, “Are you a mouse?” Brielle loves to play outside and is usually a chatty, happy-go-lucky little girl. But, sometimes, she can be overwhelmed by the excitement of gathering with family and friends.

Brielle was born with what’s known as a port-wine birthmark on her face. It is aptly named for its dark reddish color. Port-wine birthmarks can be present on otherwise healthy babies. But Heather and her husband, Justin, quickly learned that this type of birthmark can alternatively be symptomatic of a worrisome underlying condition. …

Sporting a Superman sock on her left foot and Batman on her right, Bella Burton, a 12-year-old from Woburn, Massachusetts, listens intently to her orthopedic surgeon Dr. Lawrence Karlin. Lots of people mix up their socks, he tells her. “You should really stand out from the crowd. Wear unmatched shoes.”

She chuckles and pretends to ponder his advice. Ultimately, Bella decides against Karlin’s fashion tips.

The exchange is typical of Bella and Karlin, says her mother Rachel.

The pair first met in 2007 at the Boston Children’s Hospital Orthopedic Center when Bella was just a toddler. Genetic experts suspected Bella had Morquio syndrome, a rare birth defect whose symptoms include abnormal bone and spine development and possible heart and vision problems.

As Bella underwent genetic testing, Rachel and her husband Ed faced a flutter of uncertainty. “We were so new to Boston Children’s, and Bella’s diagnosis wasn’t confirmed.”

Dan and Alex, a few weeks after Alex’s surgery for Gorham-Stout disease (Photo Susanne Malloy)

On a snowy Saturday in January, two mothers sat sipping tea and conversing about their sons. It was an ordinary scene, but the women’s conversation was far from ordinary.The scariest thing a doctor can tell you is ‘I don’t know. I’ve never seen this before.’ To find two doctors who treated this before and then to see Dan doing so well is tremendously gratifying. ~ Susanne Malloy

Susanne’s son Alexander Malloy, 14, had been recently diagnosed with Gorham-Stout disease. Gorham-Stout, also referred to as “vanishing-bone” disease, triggers a process that destroys bones and typically affects a single area like the shoulder, jaw hip, rib or spine.

“It was shocking,” recalls Susanne. An MRI earlier that week, prompted by a worsening of her son’s mild scoliosis, had shown Alex was missing bones in his spine and likely had Gorham-Stout.

After the MRI, Alex’s orthopedic surgeon, Dr. Lawrence Karlin, reassured Susanne and her husband Tom that Boston Children’s Hospital would have a plan for their son.

As Susanne and Tom digested the diagnosis, she began thinking Gorham-Stout, a rare bone disease of the lymphatic system reported in about 300 patients, sounded familiar. “I can’t have heard of it before,” she told herself.

The feeling persisted, so she called a friend, who said, “That sounds like Dan Ventresca.”

Twelve years earlier, Dan, who lived a few streets away from the Malloys in Hingham, Massachusetts, had been diagnosed with the same disease. Like Alex, Dan’s disease was located in his spine. Susanne’s friend called Dan’s mother. …

Mother’s Day 2010: I watch as my mother unwraps the first of her presents. It is pair of pretty handmade slippers. She is pleased. I am anxious, though. As I watch her sweetly looking over the slippers, I try to resist the urge to push the next package toward her and demand she open it immediately.

I quite literally sit on my hands to keep myself in check.

When she finally unwraps the second package, I watch the confusion on her face as it settles into a hopeful realization. She holds up the tiny little slippers and asks, “Are you?” I smile and nod, tears welling up in my eyes, “It is really early mom, but we wanted you to know … Happy Mother’s Day!”

I am four weeks pregnant, expecting my first child, my mother’s first grandchild. I can already imagine what it will feel like, one year later, celebrating my first Mother’s Day. Mom and I will sit under the big umbrella our faces and arms in the shade, our feet in the sun. We’ll pass the baby back and forth, laughing and talking about this baby’s future. We’ll walk around mom’s gardens and admire the flowers. We’ll already be a little clan: mom, me and my baby girl — she will be a girl, I just know it.

I am right. The little tiny bundle of cells and joy growing inside me is a little girl, just as I imagined.

But, also, she is already unbelievably different than I ever could have imagined.

Mother’s Day 2011: I glance over my sleeping three-month-old daughter Esmé. I take her in completely — her full head of dark hair, her pouty lips, her dimpled hands. For a moment I swim in the calm of watching her little chest rising and falling rhythmically — in and out, in and out.

After a beat, I snap to, scanning the lines running from her, glancing over the IV, oxygen and monitors. I have the same thought I have had every morning for the last week: She made it through another night.…